BBC Travel News

Portuguese airline TAP cancelled a number of flights between London and Lisbon, Porto and Madeira, as well as one Lisbon-Manchester service. A service arriving from and returning to Brussels out of Newcastle airport was also cancelled on Wednesday morning.

There were delays to some Easyjet flights, including a London-to-Greece service that departed three hours and 40 minutes late.

The airline said: "We are proactively trying to minimise disruption. However, we would like to warn customers that they could experience delays to their travel plans."

British Airways said customers on Spain flights on Wednesday could re-book free of charge, while there would be full refunds for cancellations.

"We are also looking at putting on larger aircraft to help as many customers as possible," the airline added.

"We are advising customers to check ba.com for the latest flight information. We apologise to our customers for any inconvenience caused by industrial action, which is beyond our control."

Unions in Spain and Portugal started strikes at midnight to protest against austerity measures that have combined tax rises with cuts in salaries, pensions, benefits and social services.

The protests have led to outbreaks of violence in several Spanish cities.

In Greece, the strike action is the third major walkout in two months.